Vortex-lattice melting and paramagnetic depairing in the nematic superconductor FeSe
Vortex-lattice melting and paramagnetic depairing in the nematic superconductor FeSe
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向列超导体 FeSe 中的涡晶格熔化和顺磁性脱配对
DOI：
10.1103/physrevresearch.2.033319
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发表时间：
2020-08-27
影响因子：
4.2
通讯作者：
Marcenat, C.
中科院分区：
文献类型：
--
作者：
Hardy, F.;Doussoulin, L.;Marcenat, C.
在超导体FeSe的完整的H-T相图映射出使用比热和热膨胀测量下降到0.7 K和高达30 T的两个磁场方向。一个明确的热力学信号的一个潜在的涡融过渡被发现在这两个数据集，并可以遵循到低温。尺度分析表明存在显著的高斯热超导涨落，并给出了平均场上临界场Hc 2（T）。对于两种场取向，Hc 2（T）都表现出Pauli限制行为。尽管霍顿等人的模型很好地描述了涡旋熔化线的温度依赖性，Phys. Rev. B 40，6763（1989）中所述的方法，降低到H？FeSe层的涡旋熔化线表现出不寻常的行为，平行于平面的领域，泡利限制强得多。在此，仅在T*=2-3 K下观察到涡旋熔化异常，然后如阿达奇和Ikeda，Phys. Rev. B 68 184510（2003）所预测的与Hc 2（T）线合并。在T以下，Hc 2（T）也表现出轻微的上升，可能与Fulde-Ferrell-Larkin-Ovchinnikov（FFLO）态的发生有关。
The full H-T phase diagram in the nematic superconductor FeSe is mapped out using specific-heat and thermal-expansion measurements down to 0.7 K and up to 30 T for both field directions. A clear thermodynamic signal of an underlying vortex-melting transition is found in both datasets and could be followed down to low temperatures. The existence of significant Gaussian thermal superconducting fluctuations is demonstrated by ascaling analysis, which also yields the mean-field upper critical field Hc2(T). For both field orientations, Hc2(T) shows Pauli-limiting behavior. Whereas the temperature dependence of the vortex-melting line is well described by the model of Houghton et al., Phys. Rev. B 40, 6763 (1989) down to the lowest temperatures for H ? FeSe layers, the vortex-melting line exhibits an unusual behavior for fields parallel to the planes, where the Pauli limitation is much stronger. Here, the vortex-melting anomaly is only observed down to T*=2-3 K, and then merges with the Hc2(T) line as predicted by Adachi and Ikeda, Phys. Rev. B 68 184510 (2003). Below T, Hc2(T) also exhibits a slight upturn possibly related to the occurence of a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state.